Starting-point for the invention was a problem that exists in the semi-conductor industry where ozone is used to thoroughly clean so-called wafers. In this process, the wafers which have been brought into a chamber are flushed with water, and gases with high concentrations of ozone are separately introduced into the chamber. Due to its high ozone concentration, the ozone that is not converted in the course of the cleaning process has to be completely destroyed for safety reasons. To this end, it was common to pass the gas containing ozone escaping from the wafer chamber over aluminum oxide and deozonate it by means of UV radiation in the range of 254 nm and exposure to a temperature of approximately 70° C. However, if a dose of 0.1% hydrofluoric acid is additionally introduced into the wafer chamber for cleaning purposes, a portion of which also will be discharged from the wafer chamber and thus conducted over the aluminum oxide. The aluminum oxide will instantly react with the hydrofluoric acid and will become useless.
Another method known to remove residual ozone consists in its thermal destruction at temperatures >350° C., a process characterized by a high consumption of energy. In order to minimize this high energy consumption, the prior art already suggested connecting a heat exchanger in series upstream or downstream, in order to heat up the gas. In the course of this process, the cold gas led into the device is then pre-heated with the hot, ozone-free gas discharged from the device. Thus, the full energy requirement in the form of heat energy no longer has to be brought in, instead, only the respective heat losses need to be compensated. According to the state of the art it is customary in this method to employ shell-and-tube exchangers having a coaxial arrangement of the tubes or a so-called revolver construction. However, in this case it is disadvantageous that such a tubular flow is characterized by a relatively high pressure drop and accordingly requires a large structural volume.
In order to destroy ozone in an aircraft environmental control system, U.S. Pat. No. 7,037,878 proposes a catalytic converter with a staggered arrangement of rib-shaped elements having a coating consisting of the catalyst and anodized layers on one face. The anodized layers serve as a support for the catalyst, providing an additional surface for an improved distribution of the catalyst. After leaving the converter, the airflow thus cleared of ozone is conducted over a heat exchanger, the construction of which is not being mentioned in further detail.
From U.S. Pat. No. 6,328,941, the use of recuperative heat exchangers has become known to be applicable in the thermal decomposition of N2O in gases containing N2O. Temperatures of from 800 to 1,200° C. are required for this thermal decomposition.
The heat exchanger has solid-bed bulk material composed of inert particles, e.g. Al2O rings that are heated up to the required working temperature.
The heat exchanger is thus a reaction chamber and heat exchanger in one. The converted gas is cooled down by means of heat exchange, while the heat-carrying elements and the new gas to be converted preheated.
In addition, a method for a very specialized application has become known from U.S. Pat. No. 6,848,501, to prevent clogging in a plate heat exchanger developed for heating and cooling of a gas containing deposit-forming components. This gas is released in the process of producing (meth)acrylic acid or (meth)acrylic acid esters. The plate exchanger is modified in such a way that its flow-through width is exactly defined and its inlet is provided with a gas dispersion plate.